One of the best tools to work with your server is included right on your Mac. It is called Network Utility and it’s located in the Utilities folder. (Located in Applications, or press Shift+Command+U in Finder.)
With this application, you can do things like Name Server lookups, Whois lookups, Traceroutes, Port Scans, etc. Alot of these same tasks can be done in Terminal as well, but Network Utility sure makes it easy.